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Rao G.A.,University of South Carolina | Rao G.A.,William Jb Dorn Veterans Affairs Medical Center | Mann J.R.,University of South Carolina | Bottai M.,University of South Carolina | And 7 more authors.
Journal of Clinical Pharmacology | Year: 2013

To address concerns regarding increased risk of prostate cancer (PrCA) among angiotensin receptor blocker (ARB) users, we used national retrospective data from the Department of Veterans Affairs (VA) through the Veterans Affairs Informatics and Computing Infrastructure. We identified a total of 543,824 unique Veterans who were classified into either ARB treated or not-treated in 1:15 ratio. The two groups were balanced using inverse probability of treatment weights. A double-robust cox-proportional hazards model was used to estimate the hazard ratio for PrCA incidence. To evaluate for a potential Gleason score stage migration, we conducted weighted Cochrane-Armitage test. Post weighting, the rates of PrCA in treated and not-treated groups were 506 (1.5%) and 8,269 (1.6%), respectively; representing a hazard ratio of (0.91, p-value .049). There was no significant difference in Gleason scores between the two groups. We found a small, but statistically significant, reduction in the incidence of clinically detected PrCA among patients assigned to receive ARB with no countervailing effect on degree of differentiation (as indicated by Gleason score). Findings from this study support Food and Drug Administration's recent conclusion that ARB use does not increase risk of incident PrCA. © The Author(s) 2013.

Rao G.A.,University of South Carolina | Rao G.A.,William Jb Dorn Veterans Affairs Medical Center | Rao G.A.,Columbia College at South Carolina | Mann J.R.,University of South Carolina | And 11 more authors.
Annals of Family Medicine | Year: 2014

PURPOSE Azithromycin use has been associated with increased risk of death among patients at high baseline risk, but not for younger and middle-aged adults. The Food and Drug Administration issued a public warning on azithromycin, including a statement that the risks were similar for levofloxacin. We conducted a retrospective cohort study among US veterans to test the hypothesis that taking azithromycin or levofloxacin would increase the risk of cardiovascular death and cardiac arrhythmia compared with persons taking amoxicillin. METHODS We studied a cohort of US veterans (mean age, 56.8 years) who received an exclusive outpatient dispensation of either amoxicillin (n = 979,380), azithromycin (n = 594,792), or levofloxacin (n = 201,798) at the Department of Veterans Affairs between September 1999 and April 2012. Azithromycin was dispensed mostly for 5 days, whereas amoxicillin and levofloxacin were dispensed mostly for at least 10 days. RESULTS During treatment days 1 to 5, patients receiving azithromycin had significantly increased risk of death (hazard ratio [HR] = 1.48; 95% CI, 1.05-2.09) and serious arrhythmia (HR = 1.77; 95% CI, 1.20-2.62) compared with patients receiving amoxicillin. On treatment days 6 to 10, risks were not statistically different. Compared with patients receiving amoxicillin, patients receiving levofloxacin for days 1 to 5 had a greater risk of death (HR = 2.49, 95% CI, 1.7-3.64) and serious cardiac arrhythmia (HR = 2.43, 95% CI, 1.56-3.79); this risk remained significantly different for days 6 to 10 for both death (HR = 1.95, 95% CI, 1.32- 2.88) and arrhythmia (HR = 1.75; 95% CI, 1.09-2.82). CONCLUSIONS Compared with amoxicillin, azithromycin resulted in a statistically significant increase in mortality and arrhythmia risks on days 1 to 5, but not 6 to 10. Levofloxacin, which was predominantly dispensed for a minimum of 10 days, resulted in an increased risk throughout the 10-day period.

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